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Electrorefining and Electrochemistry of Molten Iron and Iron-Carbon Electrodes in Slag.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Electrorefining and Electrochemistry of Molten Iron and Iron-Carbon Electrodes in Slag./
Author:	Judge, William David.
Description:	1 online resource (270 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 83-01, Section: A.
Contained By:	Dissertations Abstracts International83-01A.
Subject:	Engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28320731click for full text (PQDT)
ISBN:	9798522943363

Electrorefining and Electrochemistry of Molten Iron and Iron-Carbon Electrodes in Slag.
Judge, William David.

Electrorefining and Electrochemistry of Molten Iron and Iron-Carbon Electrodes in Slag. - 1 online resource (270 pages)

Source: Dissertations Abstracts International, Volume: 83-01, Section: A.

Thesis (Ph.D.)--University of Toronto (Canada), 2021.

Includes bibliographical references

Despite a perpetual societal need for steel, the industry is facing critical challenges as more steel must be continually recycled to improve sustainability and close material loops in circular economies. A major issue here is producing high-value products and controlling elements like carbon in the face of stringent consumer requirements, volatile markets, low profit margins, and scrap irregularity. In this dissertation, a new electrorefining process was developed where molten iron is decarburized by imposing an electromotive force between it and a slag electrolyte at 1600-1700 °C.Upon anodic polarization, oxygen-containing anions react with carbon dissolved in molten iron, evolving gaseous carbon monoxide. As carbon is oxidized from the iron anode, valuable metallurgical-grade silicon is recovered as a by-product on counter electrodes. Electrorefining trials were conducted over the entire compositional range from 4.5 to 0.005 wt% C and shown capable of producing high-value ultra-low carbon steel containing <0.001 wt% C. The process has low energy input, requires no reagents, and is self-mixing. Techno-economic analysis and benchmarking against conventional technology shows electrorefining may have competitive advantage in the low carbon range. As an electrochemical technology, electrorefining is fast adapting, flexible, scalable, and integrable with mini-mills that recycle steel with electric furnaces.Mechanisms and kinetics of electrode processes were investigated in detail. Decarburization was shown to proceed by direct, interfacial reaction with carbon through a three-step mechanism. Theory of consecutive electrochemical reactions was used to derive diagnostic criteria and identify the rate-determining step based on Tafel slopes and reaction orders. Impedance spectroscopy and gas chromatography were used as accessory methods to determine surface concentrations of intermediates during anodic polarization. Several fundamental physiochemical properties were measured for the first time including standard heterogeneous rate constants, the Nernst diffusion layer thickness, differential capacitance curves, potentials of zero charge, excess charge density curves, electrocapillary curves, and the Esin-Markov coefficient of carbon in molten iron. Although it is well known carbon is not surface active at the metal/gas interface, carbon is shown to be capillary active at the slag/metal interface, expediting its removal upon application of electromotive force between the phases.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798522943363Subjects--Topical Terms:

586835
Engineering.
Subjects--Index Terms:

DecarburizationIndex Terms--Genre/Form:

542853
Electronic books.

Electrorefining and Electrochemistry of Molten Iron and Iron-Carbon Electrodes in Slag.
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500 $a Source: Dissertations Abstracts International, Volume: 83-01, Section: A.
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500 $a Advisor: Azimi, Gisele.
502 $a Thesis (Ph.D.)--University of Toronto (Canada), 2021.
504 $a Includes bibliographical references
520 $a Despite a perpetual societal need for steel, the industry is facing critical challenges as more steel must be continually recycled to improve sustainability and close material loops in circular economies. A major issue here is producing high-value products and controlling elements like carbon in the face of stringent consumer requirements, volatile markets, low profit margins, and scrap irregularity. In this dissertation, a new electrorefining process was developed where molten iron is decarburized by imposing an electromotive force between it and a slag electrolyte at 1600-1700 °C.Upon anodic polarization, oxygen-containing anions react with carbon dissolved in molten iron, evolving gaseous carbon monoxide. As carbon is oxidized from the iron anode, valuable metallurgical-grade silicon is recovered as a by-product on counter electrodes. Electrorefining trials were conducted over the entire compositional range from 4.5 to 0.005 wt% C and shown capable of producing high-value ultra-low carbon steel containing <0.001 wt% C. The process has low energy input, requires no reagents, and is self-mixing. Techno-economic analysis and benchmarking against conventional technology shows electrorefining may have competitive advantage in the low carbon range. As an electrochemical technology, electrorefining is fast adapting, flexible, scalable, and integrable with mini-mills that recycle steel with electric furnaces.Mechanisms and kinetics of electrode processes were investigated in detail. Decarburization was shown to proceed by direct, interfacial reaction with carbon through a three-step mechanism. Theory of consecutive electrochemical reactions was used to derive diagnostic criteria and identify the rate-determining step based on Tafel slopes and reaction orders. Impedance spectroscopy and gas chromatography were used as accessory methods to determine surface concentrations of intermediates during anodic polarization. Several fundamental physiochemical properties were measured for the first time including standard heterogeneous rate constants, the Nernst diffusion layer thickness, differential capacitance curves, potentials of zero charge, excess charge density curves, electrocapillary curves, and the Esin-Markov coefficient of carbon in molten iron. Although it is well known carbon is not surface active at the metal/gas interface, carbon is shown to be capillary active at the slag/metal interface, expediting its removal upon application of electromotive force between the phases.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2023
538 $a Mode of access: World Wide Web
650 4 $a Engineering. $3 586835
650 4 $a Materials science. $3 543314
650 4 $a Design. $3 518875
650 4 $a Electrolytes. $3 656992
650 4 $a Gases. $3 559387
650 4 $a Electrodes. $3 629151
650 4 $a Hypotheses. $3 3560118
650 4 $a Experiments. $3 525909
650 4 $a Calibration. $3 2068745
650 4 $a Metallurgy. $3 535414
653 $a Decarburization
653 $a Electrochemistry
653 $a Electrorefining
653 $a Impedance
653 $a Slag
653 $a Steelmaking
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710 2 $a University of Toronto (Canada). $b Materials Science and Engineering. $3 2093675
773 0 $t Dissertations Abstracts International $g 83-01A.
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